One popular type of metal roof is generally referred to in the industry as a standing seam metal roof. In a standing seam metal roof, the longitudinal edges of the individual metal panels have relatively complex configurations which allow for an interlocking relationship with an adjacent and similarly formed panel. The region of the interlock extends upwardly from the roof to define a "standing seam" which runs parallel with the pitch of the roof. A plurality of clips are secured to each of the standing seams at spaced locations and are interconnected with the underlying support structure. Based upon the type of interlocking relationship between adjacent panels used in standing seam roofs, the panels are able to slide relative to each other to a degree and the substructure along the seam to accommodate, for instance, for thermal expansion and contraction. Notwithstanding the performance benefits of standing seam roofs, the panels themselves are relatively expensive and the labor costs for installing these types of roofs is relatively high since specially trained installers are normally utilized.
Another type of metal roof is commonly referred to in the industry as a nestable/trapezoidal/through-fastened/face-fastened roof (hereinafter "nestable roofs"). Panels for forming nestable roofs generally have ribs or crowns of varying configurations which run parallel with the pitch of the roof with a lower base or pan portion therebetween. These types of metal panels are typically manufactured from relatively thin gauge metal in a variety of widths and lengths and are significantly less expensive than standing seam roof panels since there are no complex configurations on the longitudinal edges of the panels. That is, adjacent panels are merely placed in an overlapping relation and secured to the substructure. In this regard, these types of metal panels have traditionally been installed by fastening the panels directly to the substructure by driving screws or the like directly through one or more of the base or pan portions of each panel. Consequently, installation costs are significantly lower than those associated with standing seam roofs since specially trained installers are not required.
Although economic considerations favor nestable roofs over standing seam roofs, performance considerations still favor standing seam roofs. That is, due to the manner in which the nestable roofs are installed, the nestable roof does not adequately account for thermal expansion and contraction. That is, there is resistance to movement of the individual panels in a nestable roof in a direction parallel with the pitch of the roof, primarily where the individual panels are pinned to the substructure in the above-noted manner. Consequently, these types of movements have a tendency to produce cracks or tears in the panels where pinned to the substructure and may also damage the substructure itself. Therefore, the potential for developing undesirable leaks is relatively significant in nestable roofs. This is compounded by the fact that the locations of attachment (i.e., the base or pan portion of the panel which is the lowest part of the panel) is in the drainage plane of the roof.
Based upon the foregoing, there is a need for an intermediately priced metal panel roof system, primarily one which has some of the performance attributes of a standing seam roof with regard to expansion/contraction capabilities, as well as some of the economic attributes of a nestable roof.